In the past, as a method for compensating conversion gain error, a feedback loop was used as a structure for calculating difference of the amplitudes of in-phase signals and quadrature signals and amplifying the amplitude of the in-phase or quadrature signals so as to make the calculation result to be zero (for example, Patent document 1). Also in the past, as receiver architecture, sub-sampling in an A/D (analogue/digital) converter was used (for example, Patent document 2). Furthermore, in the past, as a method for compensating phase mismatch, orthogonality was detected by calculating the product of in-phase signals (I) by quadrature signals (Q) and finding out their cross correlation (for example, Non-patent document 1).
[Patent document 1] Japanese Unexamined Patent Application Publication No. 2003-258931
[Patent document 2] Japanese Unexamined Patent Application Publication No. 2003-318759
[Non-patent document] Behzad Razavi, ‘design Considerations for Direct-Conversion Receivers’, IEEE Transaction on Circuits and Systems II, vol. 44, no. 6, pp. 428-435, 1997